Which mason_data to clear when installing plugins?

Hello list,
I’m installing the HistoryFilter plugin as suggested in my last thread. As
I was going to clear the cache, I found something odd: I appear to have two
mason caches. One is for RT while the other isn’t explicitly so, but
still… Which one should I clear out? I see:

/var/cache/request-tracker4/mason_data, inside of which are obj, cache, and

/var/cache/mason, inside of which are obj and cache

The first one seems the obvious choice, but I had no end of trouble getting
ExtensionAsString to work when I tried it last week. I wonder if I was
clearing out the wrong cache? What’s the worst that happens if I clear the
wrong one (one not meant for RT)? I’m guessing nothing too bad, as this is
just a cache anyway. Oh, I’m on Debian 8, RT4.2.8, everything up to date.

Alex Hall
Automatic Distributors, IT department